Method of hydrodesulfurizing olefinic gasoline using an iron oxide-chromium oxide catalyst



2,891,003 Patented June 16, 1959 METHOD OF HYDRODESULFURIZING OLEFINICGASOLINE USING AN IRON OXIDE-CHROMIUM OXIDE CATALYST Michael C.Chervenalr, Trenton, Percival C. Keith, Peapack, and Helmut R. Pichler,Trenton, N.J., assignors to Hydrocarbon Research, Inc., New York, N.Y.,a corporation of New Jersey No Drawing. Application March 15, 1954Serial No. 416,446

9 Claims. (Cl. 208--216) This invention relates to the treatment ofhydrocarbon oils and is more particularly concerned with the treatmentof raw cracked gasoline fractions. The invention is concerned primarilywith the treatment of raw cracked gasoline fractions to produce finishedgasoline of commercial motor gasoline likewise required that it pass anexistent gum test, in accordance with ASTM method D38l50, in which thegasoline must show less than mg. of gum per 100 ml. In addition, it ishighly desirable that commercial motor gasoline meet the storagestability requirements set forth in ASTM methods D910- 52T or D525-49.Finally, the demands of modern high compression engines make necessarythe production of motor gasoline possessing a high octane rating,usually determined as clear research octane number in accordance withASTM method D908-48T. In recent years, motor gasolines sold in many U.S.cities have had research octane ratings of approximately 83 and 90 forregular and premium gasolines, respectively, with such gasolinescontaining anaverage of 1.35 and 1.75 cc./gal., respectively, oftetraethyl lead.

In modern petroleum refining practice, it is highly advantageous toconvert part or all of the higher boiling fractions of the crude oil tomaterials boiling in the gasoline range. This is effected by processeswhich involve the cracking of the higher boiling hydrocarbons intohydrocarbons boiling in the gasoline range. However, in many cases, thegasoline fraction which is produced by cracking (hereinafter referred toas raw gasoline) requires further processing to provide a commerciallyacceptable product having a sulfur content, storage stability and octanenumber within the above specified limits. Various processes have beenproposed for treating such raw gasoline fractions to bring them withinthe desired specification limits, and some of these processes have beencommercially used with varying effectiveness.

While sulfur compounds are found in varying amounts in petroleum crudesor fractions, the amount of such compounds often exceeds a valuecorresponding to 1.0% by weight of sulfur. When such a crude or crudefraction is cracked, the raw gasoline product thereby obtained may notmeet the above limits with respect to sulfur content. Furthermore, thesulfur compounds in the raw gasoline often exist as thiophenes andcompounds of similar cyclic structure. Such cracked raw gasolines aregenerally of moderate to high octane number, containing 10 to 50% byvolume of aromatic hydrocarbons and at least 20% by volume of olefins.Known methods for removing cyclic sulfur compounds bring about thedestruction or conversion of some of these unsaturated hydrocarbons. Forexample, when hydrogenation at relatively high pressures and relativelylow temperatures is employed, the olefins present in the crackedgasoline are completely hydrogenated to paraffins, i.e.

It is Well known that such paraflins have clear research octane numberswhich are as much as 40 octane numbers lower than the correspondingolefins from which they were formed. Thus, such treatment of a rawcracked gasoline fraction produces a finished gasoline which isgenerally of appreciably lower clear research octane number than the rawgasoline, and which is in all cases of lower clear research octanenumber than would have been obtained if said olefins had not beenhydrogenated. Where the cracking operation produces a raw gasoline whichsatisfies octane number requirements without the addition of tetraethyllead, e.g., above 83 clear research octane number, such utilization ofconventional hydrogenation treatment to remove cyclic sulfur compoundsresults in a finished gasoline which is of considerably re duced clearoctane number and which consequently requires significant quantities ofanti-knock additives to achieve octane requirements. Thus, the principalproblem which these cracked raw gasoline fractions of high octane numberand high sulfur content present is the reduction of sulfur content tocommercially acceptable limits without adverse effect upon the clearresearch octane number. Similarly, when such cracked raw gasolinefractions are relatively unstable, it is necessary to increase theirstability to the desired extent without adverse efiiect upon the otherproperties of the gasoline. These are problems which have not beensolved in a satisfactory and elficient manner by prior processes fortreating raw gasoline.

A principal object of the present invention is to provide a process fortreating raw gasoline fractions containing at least 20% by volume ofolefins and more than 0.1% by weight of sulfur as thiophenic or othercyclic sulfur compounds, which process will eliminate a substantialportion of said sulfur compounds, while maintaining the major portion ofsaid olefins.

It is a further important object to provide a process for treating saidraw gasoline fractions, which will eliminate a substantial portion ofsaid sulfur compounds, while increasing or at least maintaining theoctane ratings of said raw gasolines.

It is another object of the invention to provide a process of thecharacter indicated which is also effective simultaneously to increasethe stability of such raw gasoline fractions.

Still another object is to provide an improved cracked raw gasolinetreating process which avoids the shortcomings of treating processesheretofore proposed.

It is a feature of the invention that cracked raw gasoline is treated atan elevated temperature and at a me determined hydrogen partial pressurein the presence of a material having catalytic activity to convertrefractory cyclic sulfur bodies into readily separable compounds, andgum-forming bodies into stable hydrocarbons. This treatment does notsignificantly decrease the clear research octane number of the rawcracked gasoline, even when the octane number exceeds 80. In many cases,the process of this invention increases the octane number. Thus, theapplication of this process to raw lgasolines of clear research octanenumber exceeding 80. makes it possible to meet commercial octanerequirements without the addition of ani-knock agents.

In accordance with the invention, a cracked raw gasoline fractioncontaining over 0.1% by weight of sulfur as thiophenes and other cycliccompounds, and containing at least 20% by volume of olefins, isintroduced, to-

gether with hydrogen, into a treating zone maintained at a temperatureof 750 to 1000".F., preferably at a temperature of about 800 to 950? F.,in contact with particulate iron-chromium catalyst of the characterhereinbelow described. The total pressure in the treating zone and theintroduction of hydrogen and raw gasoline are controlled in known mannerto provide a hydrogen partial pressure of 50 to 250 p.s.i. (pounds persquare inch), preferably 50 to 150 p.s.i. The total pressure of thesystem may vary over a relatively wide range, but it is generallypreferred to use a total pressure not exceeding about 800 p.s.i.g.(pounds per square inch gage). The iron-chromium catalyst employed inthe treating zone is derived from a mixture of iron and chromium oxidesin which mixture the chromium oxide is the minor component. In mostinstances, the chromium oxide is in the range of 0.2 to 20% by weight ofthe catalytic oxide mixture, 0.5 to 5% by weight of chromium oxide beingfrequently optimum. Such catalytic mixtures have been readily preparedby the co-precipitation of the iron and chromium oxides in the plusthree valence states.

It is noteworthy that the catalyst of this process does not require asupport or carrier. In fact, iron-chromium oxide mixtures supported bycarriers have been found less effective than the unsupported oxides.

It is an outstanding advantage of this invention that the hydrogensupplied to the treating zone does not need to be in concentrated orpurified form. Rather, the economic attractiveness of the process stemsin large part from the fact that commonly available hydrogen-containinggases having such components as the carbon oxides, methane and steam maybe utilized. In prior desulfunzation processes, such gaseous componentshave been product gas rich in hydrogen, carbon oxides, methane andsteam. The hydrocracking process converts heavy oils to high yelds ofraw gasoline of high octane number.

This raw gasoline is highly olefinic and contains gumforming bodies andsulfur compounds, including those of the refractory thiophenic type. Theprocess of this invention is particularly suited for the stabilizationand desulfurization of hydrocracked raw gasoline since the by- :productgas of the hydrocracking operation will satisfy the hydrogenrequirements of the. process without necessitating any refinement of thegas or any supplementation of its hydrogen content from an extraneoussource.

Another recent development which highlights the economic attractivenessof the present invention is the partial combustion of hydrocarbons withhigh-purity oxygen .to produce a gas comprising hydrogen and carbonmonoxide as the predominant components. U.S. Patent 2,491,-

518 of E. W. Riblett discloses the production of such gas. Today, thepartial combustion of natural gas with oxygen obtained by theliquefaction and rectification of air offers in many localities thecheapest source of hydrogen. Consequently, olefinc raw gasolines can nowbe desulfurized and stabilized against gum formation very economicallyby this invention utilizing as the hydrogen-containing gas the productof the partial combustion process without any intermediate treatment.

Interestingly enough, when the hydrogen-containing gas fed to thedesulfurization zone also contains carbon monoxide and water vapor inappreciable quantities, the tail gas of this process may be richer inhydrogen than the gas supplied thereto even though hydrogen is consumedor taken up by the sulfur compounds and gumforming bodies of the rawgasoline undergoing treatment. This is possible in the present processbecause the ironchromium oxide catalyst iscapable of promotingsimultaneously desulfurization and the water-gas shift reaction:

There is reason to believe that treating raw gasoline pursuant to thisinvention with gas that undergoes the watergas shift reaction isparticularly desirable because nascent hydrogen will more readily attachthe sulfur and gumtforming compounds.

The hydrogen-containing gas will preferably comprise at least about 20%by volume of hydrogen in order to avoid the necessity of passingexcessively large amounts of gas through the reaction zone to providethe desired hydrogen partial pressure of 50 to 250 p.s.i. and in orderto avoid the necessity of raising the total pressure of the system to ahigh value. The amount of hydrogen supplied to the treating or reactionzone generally falls in the range of 1000 to 5000 standard cubic feetper barrel of raw gasoline, approximately 2000 standard cubic feet perbarrel being in many instances adequate.

Treatment of the cracked raw gasoline. in the reaction zone under thespecified conditions is carried out to an extent sufllcient to reducethe sulfur content of the raw gasoline and to improve its stability tothe desired degree. Advantageously, the desired reaction is insured byemploying a raw gasoline feed rate in the range of 0.3 to 3, preferably0.5 to 1.5, volumes of liquid per hour per volume of catalyst.

The term gasoline fraction" as herein used has its conventional meaning,viz., hydrocarbon fraction boiling Within the temperature range of 90 to400 F., although it will be apparent that the treating process of thisinvention is applicable to hydrocarbon fractions in which ma,- terialboiling withinthe gasoline range comprises the predominant portion ofthe fraction.

Cracked raw gasoline fractions from various sources are advantageouslytreated in accordance with the process of the invention but the improvedprocess is of particular value, as already mentioned, in reducing thesulfur content of hydrocracked raw gasoline fractions of relatively highoctane number, e.g., clear research octane numbers of about to 90,containing substantial quantities of mono-olefins. Frequently, theolefins amount to at least 30% by volume of the raw gasoline. Aspreviously pointed out, the present process is effective to remove evenlarge proportions of sulfur bodies, including thiophenes and similarcyclic compounds, without any appreciable change of the high octanenumber of the raw gasoline. In some cases the octane number is notlowered by more than one or two units, whereas in other cases it isincreased by such an amount.

Without tying the invention to any particular theory of operation, theprocess appears to involve the following types of reactions which takeplace more or less simultaneously. Thiophenes and related cyclic sulfurcompounds are converted to normally gaseous sulfur compounds likehydrogen sulfide, and diolefins are con.- verted to mono-olefins. At thesame time, aromatic hydrocarbons are not affected and only mildhydrogenation of mono-olefins takes place so that the excellentantiknock properties of the raw gasoline are not impaired.

Under the conditions of this process there is such limitedpolymerization or other degradation of the gasoline hydrocarbons thatthe deposition of carbo- 'naceous matter on the catalyst may be held toless than about 0.5% by weight of the raw gasoline and often to lessthan about 0.1%. Thus, the catalyst may be used for long periods withoutregeneration to effect removal of the carbonaceous deposit. 'Forinstance, operating the process with a fixed bed of iron-chromium oxidecatalyst and a raw gasoline feed rate of 1 liquid volume per hour pervolume of catalyst, the on-stream time will be over 1 hour and may be asmuch as a day; regeneration of the catalyst after 6 to 9 hours ofoperation will probably be adequate in most cases. At the same time, nohighboilinghydrocarb'ons are formed so that the treated gasoline doesnot require fractionation to separate out any polymers or heavyhydrocarbons. The treated gasoline wiligenerally amount to at leastabout 97% by volume of the raw gasoline.

The effluent from the treating zone will contain vapors of the gasolinehydrocarbons admixed with more volatile compounds including readilyremovable sulfur compounds formed by the breakdown of thiophenes andlike refractory sulfur compounds in the reaction zone.

The finished gasoline fraction recovered from the reaction effluent isof low sulfur content, high stability and high octane number and meetsthe specifications for commercial motor gasoline notwithstanding thepresence of a substantial quantity of sulfur compounds and diolefinsoriginally in the cracked raw gasoline. The sulfur content of thefinished gasoline can be reduced to below 0.1% by weight by the presentprocess, as well as below the 0.3% by weight level presently acceptedfor marketable motor gasoline.

The particular apparatus used for the process and the particular methodof regenerating the catalyst form no part of the present invention andany convenient apparatus and method of catalyst regeneration may beemployed. In regenerating the catalyst care must be taken, however, inaccordance with commercial regeneration techniques, to avoid the use oftemperatures which destroy or adversely alfect the catalyst. In theregeneration of the catalyst of the present process, temperatures inexcessof 1100 F. are generally to be avoided.

In order to facilitate the maintenance of the desired temperature in thereaction zone, the raw cracked gasoline to be treated is advantageouslypreheated to a temperature of 400 to 800 F., preferably about 500 to 700F., before being fed into the reaction zone. At such temperatures thegasoline is at least partially vaporized. The hydrogen-containing gasmay also be preheated to about the same temperature as the gasoline.

For a further understanding of the invention, reference is made to thefollowing specific examples which are intended as illustrative and notlimitative of the process.

Example 1 A raw gasoline obtained by vis-breaking a Kuwait residuumcontains 1.1% by weight of sulfur largely in the form of refractorycompounds and 25% by volume of olefins.

This raw gasoline and hydrogen-containing gas are brought into contactwith a catalyst composed of 95% by weight of iron oxide and 5% by weightof chromium oxide, the mixed oxides having been coprecipitated. The gasis derived by the partial combustion of natural gas with oxygen at atemperature of about 2400 F. and has an approximate composition on avolume basis, after quenching with water to 900 F.: 36% H 21% CO, 2% C1% N and 40% H 0. This gas is charged to the reaction zone at a ratecorresponding to 1800 standard cubic feet of hydrogen per barrel of rawgasoline charged therewith to maintain a hydrogen partial pressure ofabout 100 p.s.i. in the'reaction zone. The space velocity of the rawgasoline is 1.0 liquid volume per hour per volume of catalyst. Thereaction zone is maintained at a temperature of 900 F. The finishedgasoline recovered from the reaction effiuent; amounts to 98% by volumeof the raw gasoline.

The improvement, of the gasoline achieved by the process is evidentfrloma comparison of its properties, before and after treatment:

Example 2 The hydrocrac king of Kuwait residuum yields a raw gasolinecontaining about 42% by volume of olefins and a by-product gas whichcontains about 23% by volume of hydrogen, 12% carbon monoxide and 28%steam. The remainder of the gas is largely carbon dioxide and gaseoushydrocarbons, principally methane.

This gasoline of high thiophenic sulfur content together with theby-product gas is made to contact a catalyst composed of 97% by weightof iron oxide and 3% by weight of chromium oxide. The reactionconditions include a hydrogen partial pressure of p.s.i., a temperatureof 970 F. and a raw gasoline space velocity of 0.9 liquid volume perhour per volume of catalyst. The yield of finished gasoline correspondsto 96% by volume of the raw gasoline.

The proprties of the gasoline, before and after treatment, are asfollows:

Raw Finished Gasoline Gasoline Sulfur Content, wt. Percent 0.8 0.2Octane Number, OFRR Clear 88.0 86.6 Octane Number, OFRR+3 cc. TEL/ga92.0 93. 9 Oxygen Induction Time, minutes 135 435 ASTM Gum Content, nag/m1 75 2 Example 3 A raw, cracked gasoline containing 0.18% by weight ofsulfur in the form of refractory compounds and about 45% by volume ofolefins is brought into con tact with a hydrogen-containing gas and acatalyst consisting of 99.2% by weight of iron oxide and 0.8% by weightof chromium oxide. The hydrogen-containing gas consists essentially ofhydrogen, carbon monoxide and steam in the respective volume proportionsof 221:2.4 and is supplied to the reaction zone at a rate of 4,000standard cubic feet per barrel of raw gasoline charged therewith tomaintain a hydrogen partial pressure of about 100 p.s.i. in the reactionzone. The space velocity of the raw gasoline is one liquid volume perhour per volume of catalyst and the reaction tempera ture is maintainedat 925 F. 'The finished gasoline recovered from the reaction effluentamounts to 98.5% by volume of theraw gasoline.

The properties of the gasoline, before and after treatment, are asfollows:

Raw Finished Gasoline Gasoline Sulfur Content, wt. Percent 0.18 0.02Octane Number, CFRR Clear 92. 0 89. 5 Octane Number, CFRR-l-S cc.TEL/gal 97. 7 97. 5 Oxygen Induction Time, minutes 240 420 ASTM GumContent, mgJiOO m1 6. 4 0.2

7 reduction and thus supply the catalyst to the reaction in a state morenearly like that attained during operation of the process when thecatalyst reaches a high level of activity.

It is to be observed that, in addition to the removal gasolines.

In view of the various modifications of the invention which will occurto those skilled in the art upon consideration of the foregoingdisclosure without departing from the spirit or scope thereof, only suchlimitations should be imposed as are indicated by the appended claims.

What is claimed is:

1. A vapor-phase process for desulfurizing a highly olefinic hydrocarbonfraction, which comprises bringing hydrogen and a vaporized hydrocarbonfraction containing more than 1% by weight of sulfur in the form ofrefractory sulfur compounds and more than 20% by volume of olefinsimparting to said hydrocarbon fraction a high octane number into contactwith an ironchromium'oxide catalyst comprising chromium oxide in therange of 0.2 to 20% by weight of the catalytic oxide mixture in areaction zone maintained at a temperature in the range of 750 to 1000F., effecting reaction between said hydrogen and said vaporizedhydrocarbon fraction during contact with said catalyst to the extentthat there is a net consumption of hydrogen without hydrogenation of atleast a major portion of said olefins, passing said hydrocarbon fractionthrough said reaction zone at a space velocity in the range of about 0.3to 3 liquid volumes per. hour pervolume of said catalyst,

maintaining the partial pressure of hydrogen in said reaction zone inthe range of 50 to 250 p.s.i., and recovering from the resultingvaporized reaction eflluent a highly olefinic hydrocarbon fractioncontaining less than 0.3% by weight of sulfur and at least a majorportion of said olefins and having a high octane number.

2. A vapor-phase process for desulfurizing a highly olefinic hydrocarbonfraction, which comprises bringing hydrogen and a vaporized hydrocarbonfraction containing more than 0.1% by Weight of sulfur in the form ofrefractory sulfur compounds and more than 30% by volume of olefinsimparting to said hydrocarbon fraction a high octane number into contactwith an ironchromium oxide catalyst comprising chromiumoxide in therangeof 0.2 to 20% by weight of the catalytic oxide mixture in a reactionzone maintained at a temperature in the range of 800 to 950 F.,effecting reaction between said hydrogen and said vaporized hydrocarbonfraction during contact with said catalyst to the extent that there is anet consumption of hydrogen Without hydrogenation of at least a majorportion of said olefins, passing said hydrocarbon fraction through saidreaction zone at a space velocityin the range of about 0.3 to 3 liquidvolumes per hour per volume of said catalyst, maintaining the partialpressure .of hydrogen in said reaction zone in the range of 50 to 250p.s.i., and recovering from the resulting vaporized reaction effiuentahighly olefinic hydrocarbon fraction containing less than 0.1% byweight of sulfur and at least a major portion of said olefins and havinga high octane number.

3. A vapor-phase process for desulfurizing a highly olefinic gasolinefraction,'which comprises bringing hydrogen and a vaporized gasolinefraction containing more than 0.3% by weight of sulfur in the form ofrefractory sulfur compounds and more than 30% by volume of olefins andhaving a clear research octane number of at least about 80 into contactwith an ironchromium oxide catalyst comprising chromium oxide in therange of 0.2 to 20% by weight of the catalytic oxide mixture in areaction zone maintained at a temperature in the range of 800 to 950 F.,effecting reaction between said hydrogenand said vaporized gasolinefraction during contact with said catalystto the extent that there is anet consumption of hydrogen without hydrogenation of at least majorportion of said olefins, passing said gasoline fraction through said.reaction zone at a space velocity in the range of about 0.3 to 3 liquidvolumes per hour per volume of said catalyst, maintain ing the partialpressure of hydrogen in said reaction zone in the range of 50 to 250p.s.i., andrecovering from the resulting vaporized reaction efiluent ahighly olefinic gasolinefraction containing less than 0.3% by weight ofsulfur and at leasta major portion of said olefins and having a clearresearch octane number of at least about 80. i

4. A vapor-phase process according to claim 3 wherein the iron-chromiumoxide catalyst is derived by the co-precipitation of the iron andchromium oxides, and{ the hydrogen partial pressure is in. the range of50 to p.s.i.

5. A vapor-phase process according to claim 3 wherein the hydrogensupplied to the reaction zone is admixed with a substantial quantity ofa gas selected from the group consisting of carbon monoxide, carbondioxide, water vapor and mixtures thereof.

6. A vapor-phase process for refining a highly olefinic gasoline, whichcomprises bringing hydrogen and a vaporized raw gasoline containing anappreciable quantity of troublesome foreign matter of the class ofrefractory sulfur compounds and "gum-forming bodies and containing morethan 20% by volume of olefins, said raw gasoline having a clear researchoctane number .of at least about 80, into contact with aniron-chromiumoxide catalyst comprising chromium oxide in the range of 0.2 to 20% byweight of the catalytic oxide mixture in a reaction zone maintained at atemperature in the range of 800 to 950 F., effecting reaction betweensaid hydrogen and said vaporized raw gasoline during contact with saidcatalyst to the extent that there is a net consumption of hydrogenwithout hydrogenation of at least a major portion of said olefins,passing said raw gasoline through said reaction zone at a space velocityin the range of about 0.3 to 3 liquid volumes per hour per volume ofsaid catalyst, maintaining the. partial pressure of hydrogen in saidreaction zone in the range of 50 to 150 p.s.i., and recovering from theresulting vaporized reaction eflluent a highly olefinic finishedgasoline substantially free of troublesome foreign matter and containingat least 20% by volume of said olefins and having a clear researchoctane number over 80.

7. A vapor-phase process accordingto claim 6 wherein the iron-chromiumoxide catalyst isderived by the co-precipitation of the iron andchromium oxides, the chromium oxide being in the range of 05 to 5%, byweight of the co-precipitated oxides.

8. A vapor-phase process according to claim 7 wherein the gasolinepasses through the reaction zone at a space velocity in the range ofabout 0.5 to 1.5 liquid volumes per hour per volume of catalyst.

9. A vapor-phase process according to claim 7 wherein the raw gasolinecontains more than 30% by volume of olefins and the hydrogen supplied tothe reaction zone is admixed with substantial quantities of carbonmonoxide and water vapor.

References Cited in the file of thispatent UNITED STATES PATENTS2,398,919 Byrns Apr. 23, 1946 2,500,146 Fleck et a1. Mar. 14, 19502,608,521 I-Ioog Aug. 26, 1952 2,658,858 Lang et al. Nov. 10, 19532,671,754 De Rosset et a1. Mar. 9, 1954 2,774,718 Johnson et al. 1' Dec;18,1956 2,774,719- Johanson Dec. 18, 1956

1. A VAPOR-PHASE PROCESS FOR DESULFURIZING A HIGHLY OLEFINIC HYDROCARBONFRACTION, WHICH COMPRISES BRINGING HYDROGEN AND A VAPORIZED HYDROCARBONFRACTION CONTAINING MORE THAN 1% BY WEIGHT OF SULFUR IN THE FORM OFREFRACTORY SULFUR COMPOUNDS AND MORE THAN 20% BY VOLUME OF OLEFINSIMPARTING TO SAID HYDROCARBON FRACTION A HIGH OCTANE NUMBER INTO CONTACTWITH IRONCHROMIUM OXIDE CATALYST COMPRISING CHROMIUM OXIDE IN THE RANGEOF 0.2 TO 20% BY WEIGHT OF THE CATALYTIC OXIDE MIXTURE IN A REACTIONZONE MAINTAINED AT A TEMPERATURE IN THE RANGE OF 750 TO 1000*F.,EFFECTING REACTION BETWEEN SAID HYDROGEN AND SAID VAPORIZED HYDROCARBONFRACTION DURING CONTACT WITH SAID CATALYST TO THE EXTENT THAT THERE IS ANET CONSUMPTION OF HYDROGEN WITHOUT HYDROGENATION OF AT LEAST A MAJORPORTION OF SAID OLEFINS, PASSING SAID HYDROCARBON FRACTION THROUGH SAIDREACTION ZONE AT A SPACE VELOCITY IN THE RANGE OF ABOUT 0.3 TO 3 LIQUIDVOLUMES PER HOUR PER VOLUME OF SAID CATALYST, MAINTAINING THE PARTIALPRESSURE OF HYDROGEN IN SAID REACTION ZONE IN THE RANGE OF 50 TO 250P.S.I., AND RECOVERING FROM THE RESULTING VAPORIZED REACTION EFFLUENT AHIGHLY OLEFINIC HYDROCARBON FRACTION CONTAINING LESS THAN 0.3% BY WEIGHTOF SULFUR AND AT LEAST A MAJOR PORTION OF SAID OLEFINS AND HAVING A HIGHOCTANE NUMBER.